JPH05312278A - Underground conduit - Google Patents

Abstract

PURPOSE:To provide an underground conduit which is safe even where underground water level is relatively high such as soft ground and, particularly, holds the pipe body surely and not damage it even if any flood of underground water arises abruptly due to earthquake, etc. CONSTITUTION:A sand layer 3 is formed around a laid pipe body 2, and the sand layer 3 is enclosed by a sheet cloth cover 4. Also a crushed stone layer 5 is formed around the sand layer 3, and earth 6 is refilled at the uppermost portion. Thus the pipe body 2 is protected against a concentrated stress from the crushed stone layer 5 on the outside of it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an underground buried pipeline,
Particularly, it relates to an underground buried pipeline suitable for use in an area where the groundwater level is relatively high.

[0002]

2. Description of the Related Art Conventionally, when laying water supply / drainage pipes or electric conduits, etc., the soil surface is excavated to form excavation trenches, and then the soil at the trench bottom or trench wall is compacted, and then sand or sand is struck at the trench bottom. A construction method is adopted in which crushed stone or the like is laid to a certain thickness and solidified, or concrete is driven to form a foundation, and an embedded pipe is laid on the foundation to backfill.

In this case, if the ground is firm, no particular problems will occur after the construction, but the ground is weak in the riverbeds and lakes around which the ground consists of sand layers, or in landfills such as coastal areas. In addition, because it is rich in groundwater, it is located in a place where the groundwater level is relatively high. In such an area, if the piping is constructed based on the above-mentioned construction method, the buried pipe may be unevenly submerged with time, or conversely, an abnormal buoyancy may occur with respect to the buried pipe.

[0004] In particular, when an earthquake occurs, abnormal groundwater discharge and ground liquefaction due to this abnormal water discharge may be observed. As a result, similar phenomena occur suddenly and on a large scale. When such a phenomenon is repeated, an accident occurs such that the buried pipe is damaged or the connection part is disconnected.

Therefore, as a countermeasure against this, conventionally, a gravel drain (= Gravel Drein) method of laying crushed stones around a pipeline to temporarily reinforce the ground, and a CCP (= Chemical Churning Pile) in which a buried pipe is fixed by a pile ) The method of construction etc. is adopted.

[0006]

However, among the above-mentioned conventional techniques, the gravel drain method is preferable in that respect because the crushed stone alleviates the effect of water pressure to some extent, but when the crushed stone collapses due to an earthquake, However, the bending stress is apt to be received properly, and at that time, the corner of the crushed stone hits a specific portion of the pipe body, and concentrated stress acts on the pipe pipe, so that there is a risk of damaging the pipe body. In the case of the CCP method, since it is a method of artificially providing a non-liquefied layer in the deep underground, it is a sufficient measure, but it is inevitable that construction costs such as material costs and labor costs will rise. was there.

As a result of various studies, the inventors of the present invention have arranged sand as a material for solidifying the circumference of a pipeline in soft ground, instead of crushed stone which may damage the tubular body. Since it does not fix the pipeline, we found that wrapping this sand with cloth will solve the problem,
The present invention has been completed.

That is, the present invention solves the above-mentioned drawbacks of the prior art and is safe even in a place where the groundwater level is relatively high, such as in soft ground, and especially when an abnormal groundwater suddenly emerges due to an earthquake or the like. Also, the purpose of the present invention is to provide an underground buried pipeline that reliably holds the pipe body and does not damage the pipe body.

[0009]

According to the present invention, "a sand layer surrounded by a cloth is provided around a laid pipe body,
Furthermore, the gist of the present invention is "underground buried pipeline, characterized in that a crushed stone layer is provided around the sand layer."

That is, according to the present invention, a sand layer encased with a cloth is used to harden the periphery of the pipe and protect the pipe body, and the sand layer is applied to the above-mentioned differential settlement in soft ground and groundwater pressure. The main point is to prevent this by placing a crushed stone layer around the.

The pipes which are the object of the underground buried pipe of the present invention are usually circular pipes, but various pipes such as an oval pipe having a substantially elliptical shape and a polygonal pipe having a shape close to a circle are used. The pipe is the target. However, the underground buried pipeline of the present invention does not prevent its adoption in the piping construction of tubular bodies having other cross-sectional shapes.

The sand layer covered with the cloth in the present invention is
It occupies an important factor in the structure of the present invention, and it is necessary that the upper, lower, left and right sides of the circumference of the pipeline are all protected by this sand layer. The sand layer is provided in order to protect the tubular body from the crushed stone layer and to ensure the solidification around the pipeline. Further, the reason why the sand is wrapped with a cloth is to prevent the sand from moving during an earthquake and to protect the pipe body from the fluctuation when the ground changes or the like.

The means for wrapping the sand layer with the cloth is not particularly limited, but as will be described in detail in the section of the construction method described later, the sand is arranged around the pipe and wound around the sand. A method of arranging cloth around the seaweed type of sushi and wrapping it,
The method of arranging a large number of sand bags around the pipeline is excellent in workability.

As the material of the cloth, a sheet or a sand bag used in general civil engineering work is adopted as it is, and a yarn or string made of synthetic resin such as nylon or vinyl chloride having excellent strength and weather resistance is sewn as a fiber material. In addition to the above-mentioned materials, so-called "Shiro mat", which is made of "Shiro", which is an old material, is also suitable. The roughness of the texture of the cloth may be of course such that sand does not leak outside.

It is almost always sufficient that the thickness of the sand layer is at least 100 mm, and the thickness of the crushed stone layer should be 1/2 or more of the width of the sand layer (the direction perpendicular to the pipeline). You can do this.

In the present invention, it is needless to say that the crushed stone layer is provided around the sand layer by utilizing its large weight per unit volume and its large hydraulic conductivity to liquefy the ground and cause the differential settlement. The purpose is to make the pipe body endure the pushing water pressure, as in the conventional case.

In the underground buried pipeline of the present invention, around the tubular body disposed in the excavation trench, from the inside to the outside,
A sand layer and a crushed stone layer must be provided, but it is optional to lay a support material layer such as a styrofoam block layer between the sand layer and the crushed stone layer and the bottom of the excavation groove. Furthermore, when a supporting material layer made of a non-water-permeable material such as a foamed polystyrene block layer is used, it is optional to provide water holes in the supporting material layer.

[0018]

According to the present invention, since the sand layer covered with the cloth is provided around the laid pipe, and the crushed stone layer is further provided around the sand layer, when the sand directly touches the pipe. Is easy to spread sand, and in the case of a sand bag, it is easy to form a sand layer.In any case, vibrations such as groundwater pressure and earthquake are indirectly transmitted to the pipe body, It is less susceptible to bending stress and is also protected from the concentrated stress from the crushed stone layer on the outside.

Further, the crushed stone layer can reduce the influence of the differential settlement of the buried pipe and counteract the influence of the abnormal buoyancy of groundwater.

[0020]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is an enlarged sectional view showing an embodiment of the underground buried pipeline of the present invention.

In these figures, 1 has a groove width of about 17
It is an excavation ditch of 00 mm, in the bottom of the center of the ditch,
A pipe body 2 made of hard vinyl chloride resin and having a nominal diameter of 250 mm is attached.

Reference numeral 3 denotes a sand layer, and 4 denotes a cloth enclosing the sand layer 3 (a civil engineering sheet called geotextile).
Then, both end edges in the width direction of the cloth 4 having a length adapted to the standard length of the tubular body 2 are overlapped on the upper part.

The thickness of the sand layer 3 is a = 40 in the figure.
0 mm, b = 100 mm, c = d = 300 mm.
Reference numeral 5 is a crushed stone layer made of crushed stone of a commercial product (crushed stone No. 5), and the backfill soil 6 is put in the upper layer thereof, thus forming the underground buried pipeline of the present invention.

The procedure for constructing the underground buried pipeline of the above embodiment is not particularly limited as described above, but from the viewpoint of workability, the procedure shown in FIG. 2 is preferable. That is, FIG.
(A) to (D) are explanatory views schematically showing one construction method by following the construction procedure, and first, as shown in FIG. 2A, the groove bottom of the excavation groove 1 is shown. Then, crushed stones are laid in a shallow manner, and the cloth 4 is further spread and laid on it. Then, sand is spread with a predetermined thickness to form a sand layer on the lower side of the tubular body 2, on which the required number of tubular bodies 2 are placed and connected to each other.

When the connection of the tube body 2 is completed, next, as shown in FIG. 2B, sand is further piled up around the tube body 2, and then both ends of the cloth 4 are pulled up to draw the figure. Two
As shown in (c), the upper part is overlaid and the seam is
If necessary, they are simply sewn together to form the sand layer 3.

Next, crushed stones are further charged around the sand layer 3 covered with the cloth 4 to be buried up to a height slightly higher than the top of the pipe body 2 to form the crushed stone layer 5. Finally, the earth and sand 6 is backfilled on it, and the construction is completed.

In the above construction method, since the sand layer 3 is rolled up with the cloth 4 in a sushi roll manner, a considerable amount of force is required, and when a thick sand layer is formed, a certain strength is required for the cloth. It Further, in some cases, mechanical force is required for winding up.

Next, another construction method will be described with reference to FIG.
This will be described with reference to (e) to (g). First, as shown in FIG. 2 (e), a shallow crushed stone is spread over the bottom of the excavation trench 1, and sand is spread over it with a predetermined thickness to form a sand layer under the pipe 2. A required number of pipes 2 are placed on top of that and connected to each other.

After the connection of the pipe body 2 is completed, next, as shown in FIG. 2 (f), a large number of sand bags 7, 7 ...
The sand layer 3'is formed with the sand initially laid up.

Next, as shown in FIG. 2G, the sand layer 3 '
Further, crushed stones are thrown into the surroundings of the pipe body 2 to be buried up to a height slightly higher than the top of the pipe body 2 to form a crushed stone layer 5 ′, and finally, earth and sand 6 ′ are backfilled thereon. Complete the construction.

According to this construction method, the step of wrapping sand with a cloth, which is shown in FIG. 2C, among the steps in the above-mentioned construction method can be omitted.

[0032]

Industrial Applicability According to the present invention, since a sand layer covered with a cloth is provided around the laid pipe body and a crushed stone layer is provided around the sand layer, the sand is directly applied to the pipe body. When touching it, sand can be easily compacted, and in the case of a sand bag, a sand layer can be easily formed.In any case, vibrations such as groundwater pressure and earthquakes are indirectly transmitted to the pipe body. Therefore, it is less susceptible to bending stress and is also protected from the concentrated stress from the crushed stone layer on the outside.

Further, the crushed stone layer can reduce the influence of the differential settlement of the buried pipe and counteract the influence of the abnormal buoyancy of groundwater. Therefore, even when the soft ground is in normal condition, or when underground vibration such as an earthquake suddenly occurs, the buried pipeline can withstand these situations sufficiently, and the pipe body is deformed, Accidents due to these can be prevented without damaging or disconnecting the connection part.

Further, since the underground buried pipeline of the present invention has a simple structure, the construction is simple and the construction cost is low.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view showing an embodiment of an underground buried pipeline according to the present invention.

FIG. 2 is an explanatory view showing a construction procedure of the underground buried pipeline of the present invention, in which (A) to (D) show one construction procedure, and (E) to (T) of the same figure. ) Is a figure which shows another one construction procedure.

[Explanation of symbols]

 1 excavation ditch 2 tube 3, 3'sand layer 4 cloth 5, 5 'crushed stone layer 6, 6'backfill soil 7 sandbag

Claims (1)

[Claims] 1. A buried underground pipeline characterized in that a sand layer covered with a cloth is provided around a laid pipe body, and a crushed stone layer is further provided around the sand layer.